Field of the Invention
The invention relates to an optical module, an optical system, and a displaying apparatus, and particularly to a light wavelength conversion module, an illumination system, and a projection apparatus.
Description of Related Art
With advances in display technology, an ultra high pressure lamp (UHP lamp) which emits white light may be employed with a color wheel in a projection apparatus to produce red light, green light, and blue light sequentially, which allows colored display images to be provided by the projection apparatus. In addition, the projection apparatus with light emitting diodes (LEDs) which emit red light, green light, and blue light as a light source has been developed recently. However, luminous efficiencies of the LEDs are between 5% and 12%, which are far less than a luminous efficiency of a laser diode that is more than 25%. Therefore, in recent years, laser light source with a fluorescent wheel has been gradually developed as the light source of the projection apparatus.
However, the existing laser projection apparatuses generally have a problem of poor color rendering property. The main reason is that emission spectra of the fluorescent powders used in the laser projection apparatuses are mainly between 490 nm to 580 nm, and such fluorescent powders have poor performance over 600 nm. Therefore, the display images displayed by the laser projection apparatuses are insufficient in performance of red light. The color rendering property of the laser projection apparatuses are improved mainly through additionally disposing red light emitting diodes in the laser projection apparatuses currently on the market. However, such methods need additional light emitting diodes and other coupling elements, and thus increase the costs. Different illumination systems are disclosed respectively in R.O.C. Patent No. 201239508 and U.S. Publication No. 20120102126. A fluorescent powder-converting type of a light-emitting apparatus is disclosed in China Patent No. 102272953. A fluorescent powder layer, a forming method thereof, and equipment for forming the fluorescent powder layer are disclosed in China Patent No. 102272954.